Sheet metal explosion-proof, and flame-proof enclosures

ABSTRACT

An explosion retaining housing includes a sheet metal member or outer skin which at least in part forms an interior region of the housing. At least one structural element provides additional strength to the member to retain the explosion in the region. The structural element can be inside of, or, outside of the region. The structural element can have a plurality of components which cooperate together to resist the force of an explosion in the interior region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority benefit under 35U.S.C. §121 to co-pending U.S. patent application Ser. No. 12/813,667,filed on Jun. 11, 2010, and entitled “Sheet Metal Explosion-Proof, andFlame-Proof Enclosures”, which is hereby incorporated by reference forall purposes as if reproduced in its entirety.

FIELD

The invention pertains to explosion-proof, dust-ignition proof andflame-proof enclosures. More particularly, the invention pertains tosuch enclosures implemented, at least in part, with sheet metal-typehousings.

BACKGROUND

Traditional explosion and flameproof enclosures are constructed usingcast metal components. These enclosures are typically expensive, andheavy. Further, manufacture and assembly are time consuming.

Cast metal enclosures often suffer from porosity caused by blowholes andfissures leading to thick wall constructions, welded repairs andadditional pressure testing requirements of the enclosure to ensure itcan be operated safely within explosive gas and dust atmospheres. Insummary, known explosion resistant enclosures resist the explosionpressure by use of a load bearing skin, for example a cast housing.

There is a continuing need for enclosures for housing electricalequipment intended for use in explosive gas and dust atmospheres. Suchenclosures could be used to house various types of gas detectors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an embodiment of the invention;

FIG. 2 is a diagram of another embodiment of the invention; and

FIG. 3 is yet another embodiment of the invention.

DETAILED DESCRIPTION

While embodiments of this invention can take many different forms,specific embodiments thereof are shown in the drawings and will bedescribed herein in detail with the understanding that the presentdisclosure is to be considered as an exemplification of the principlesof the invention, as well as the best mode of practicing same, and isnot intended to limit the invention to the specific embodimentillustrated.

In embodiments of the invention, a thin walled explosion, dust-ignitionproof and flameproof enclosure can withstand the pressure developedduring an internal explosion of an explosive mixture, without damage.This containment prevents the transmission of the explosion to theexplosive gas and dust atmospheres surrounding the enclosure. In suchembodiments, a thin walled sheet metal structure, which is difficult toassemble using traditional fasteners while maintaining the requirementsof a flame-proof joint, can advantageously be utilized.

Structural members can be incorporated which are separate from theenclosure itself. Such members can be internal or external of therespective housing. While the external housing needs to withstand andretain the pressure of an internal explosion, the addition of one ormore additional, structural components which can provide some of thestructural integrity of the overall housing results in this requirementbeing met with a much lighter housing. For example, drawn sheet metalcan be used.

In one aspect of the invention, such housings can incorporate a thinsheet metal enclosure. Two metal end covers and are assembled using athreaded nut. Such sheet metal enclosures do not suffer from the sameporosity issues as a cast enclosure. As a result, a lighter gaugematerial can be used

In one embodiment, a clamped cylindrical design can be used to realizethe benefits previously described of a sheet metal enclosure. In adisclosed implementation, the sheet metal enclosure is formed in acylindrical form with openings at either end and clamped onto acylindrical ‘chassis’ securely with a clamping nut. The clamping nut isa structural member which withstands the pressure developed during aninternal explosion of an explosive mixture and prevents the enclosurefrom separating.

The cylindrical ‘chassis’ can include front and rear housings clampedtogether using one or more tie rods. The tie rods represent structuralmembers which can withstand the pressure developed during an internalexplosion of an explosive mixture and prevent the enclosure fromseparating. Flameproof joints can he incorporated at the interfacebetween the front and rear housing and the cylindrical sheet metalenclosure. Such joints prevent the transmission of an internal explosionto the explosive gas atmosphere surrounding the enclosure.

FIG. 1 illustrates an embodiment of the invention. An explosionresistant enclosure 10 includes a relatively thin sheet metal-likemember 12 which could have a variety of cross-sectional shapes such ascircular, oval, rectangular, or square all without limitation.Characteristic of the present invention, the member 12 would not itselfbe of a type which would be expected to contain an internal explosion inthe internal region V defined in part by the member 12. Rather, thatadditional strength is provided to the enclosure 10 by one of aninternal framework 16, illustrated in phantom in FIG. 1, or an externalframework, such as external framework 14 illustrated in FIG. 1, incombination with a separate outer skin or member 12. Those of skill willunderstand that the framework 14 provides explosion resisting strengthand need not completely enclose the outer skin 14, as discussed below.

The framework 14 could for example be of unitary construction with afirst portion 14 a joined to a second portion 14 b by a central portion14 c. The portions 14 a,b,c can be rod-like and form a frame that can inpart surround the outer skin 12. The outer, skin or, member 12 issandwiched therebetween. As appropriate, and known to those of skill inthe art, flame-proof joints could be incorporated into the enclosure 10.

The member 12 can carry in the internal region V (which might be closedin part by the framework 14) a detector 18 having a sensor 18 a, andcontrol circuits 18 b. An explosion in the region V would be containedby the framework 14, in combination with the member 12. It will also beunderstood that the type of detector 18 is not a limitation of theinvention. A variety of gas sensors can be used and come within thespirit and scope of the invention. The detector 18 can be in wired orwireless communication 20 with a displaced alarm system.

The chassis type construction of the enclosure 10 of FIG. 1 makes itpossible to use a much thinner member, or outer skin, than wouldotherwise be possible and still retain internal explosions in the regionV. The configuration 10 of FIG. 1 results in a lower cost solution whencompared to traditional explosion retaining enclosures which use priorart cast members.

Those of skill will understand that the location of the framework 14 isnot a limitation of the invention. It can he located in the internalregion V or outside thereof as illustrated in FIG. 1. Further members offramework 14 need not be directly or integrally coupled together.Variations and permutations thereof come within the spirit and scope ofthe invention.

FIG. 2 illustrates an alternate embodiment 30 of the invention. In theembodiment 30 of FIG. 2, strength adding elements are located in theexplosion-proof enclosed volume, region, V1. The assembly 30 includes asheet metal enclosure 32 which can be cylindrical, without imitation.

The enclosure 32 can be formed with openings 32 a,b and can bound inpart the internal volume or region V1. A gas detector which includes asensor S1 and associated control circuits CI can be carried on a printedcircuit board B1 in the internal volume V1.

Enclosure 32 is clamped onto a chassis 34, having elements 34 a,b of acomparable shape, for example if the enclosure 32 is cylindrical, thechassis 34 most conveniently could also be cylindrical, A clamping nut36 can be used to clamp the housing, or enclosure 32 to the chassis 34.The end 32 a of the enclosure 32 and a portion of the element 34 a canprovide a cable feed through.

The clamping nut 36 is a structural member which withstands the pressuredeveloped during an explosion in the internal region V1 due to aninternal explosive mixture. The nut 36 works to prevent the enclosure 32from separating due to the explosive pressures developed in the regionV1.

The cylindrical chassis 34 includes first and second elements 34 a,bwhich are clamped together using tie rods and screws 38 a,b. It will beunderstood that the number of tie rods is not a limitation of theinvention. In selected configurations, one or three or more tie rodscould be used instead of two as in FIG. 2 without departing from thespirit and scope of the invention.

The tie rods 38 a,b are internal structural members which withstand thepressure developed during an explosion in the internal region V1 andalso contribute to preventing the enclosure 32 from separating.

Flameproof joints 40 a,b can be incorporated at the interfaces betweenelements 34 a,b and the sheet metal enclosure 32. The joints 40 a,bprevent the transmission of an internal explosion to an explosive gasatmosphere surrounding the assembly 30.

In summary, as illustrated in FIG. 2, the load bearing chassis, or,structure of the assemblage 30 is separate and apart from the outer skin32. The load bearing chassis, for example, the nut 36 and first andsecond elements 34 a,b in combination with the internal tie rods 38 a,bform a structure which can withstand the explosive pressure of anexplosion in the region V1 and keep the outer skin 32 from separating inresponse to that pressure.

FIG. 3 illustrates an alternate embodiment 60 of the invention. In theembodiment 60 of FIG. 3, strength adding elements are located outside ofthe explosion-proof enclosed volume, region, V2. The assembly 60includes a sheet metal enclosure 62 which can he cylindrical, withoutlimitation.

The enclosure 62 can be formed with openings 62 a,b and can bound inpart the internal volume or region V2. A gas detector which includes asensor S2 and associated control circuits C2 can be carried on a printedcircuit board B2 in the internal volume V2.

Enclosure 62 is clamped between first and second elements 64 a,b whichare clamped together using external tie rods 68 a,b. It will beunderstood that the number of tie rods is not a limitation of theinvention. In selected configurations, one or three or more tie rodscould be used instead of two as in FIG. 3 without departing from thespirit and scope of the invention.

The tie rods 68 a,b are external structural members which withstand thepressure developed during an explosion in the internal region V2 andalso contribute to preventing the relatively thin walled enclosure 62from separating.

Flameproof joints 70 a,b can be incorporated at the interfaces betweenelements 34 a,b and the sheet metal enclosure 32. The joints 70 a,bprevent the transmission of an internal explosion to an explosive gasatmosphere surrounding the assembly 60.

In summary, as illustrated in FIG. 3, the load bearing structure of theassemblage 60 is separate and apart from the outer skin 62. The loadbearing external tie rods 68 a, b form and ends 64 a, b form a structurewhich can withstand the explosive pressure of an explosion in the regionV2 and keep the outer skin 62 from separating in response to thatpressure.

From the foregoing, it will be observed that numerous variations andmodifications may be effected without departing from the spirit andscope of the invention. It is to be understood that no limitation withrespect to the specific apparatus illustrated herein is intended orshould be inferred. It is, of course, intended to cover by the appendedclaims all such modifications as fall within the scope of the claims.

1. An explosion resistant enclosure comprising: a sheet metal memberformed to define, at least in part, an internal region; a gas sensordisposed within the internal region; at least one structural element,wherein the at least one structural element is coupled to the sheetmetal member; and one or more openings between the internal region andan exterior of the sheet metal member, wherein the at least onestructural element and the one or more openings are configured toprovide a flame-proof structure and retain a flame within the internalregion from propagating to the exterior of the sheet metal member. 2.The enclosure of claim 1, wherein the at least one structural element iscoupled to portions of the sheet metal member.
 3. The enclosure of claim1, wherein the at least one structural element is separate from thesheet metal member.
 4. The enclosure of claim 3, further comprising: atransparent window carried by the at least one structural element; andan explosion resistant seal disposed between the transparent window andthe at least one structural element.
 5. The enclosure of claim 1,further comprising: end covers joined by the structural element, whereinthe sheet metal member is retained between the end covers.
 6. Theenclosure of claim 1, wherein the at least one structural element iswithin the internal region, or outside of the internal region.
 7. Theenclosure of claim 1, wherein the at least one structural elementcomprises a plurality of structural elements.
 8. The enclosure of claim7, wherein at least some of the structural elements are in the internalregion, or outside of the internal region.
 9. The enclosure of claim 1,further comprising: a base; and a cover, wherein the sheet metal memberis disposed between the base and the cover, and wherein the at least onestructural element extends between the base and the cover.
 10. Theenclosure of claim 9, further comprising: a plurality of structuralelements extending between the base and the cover.
 11. The enclosure ofclaim 10, further comprising: processing circuitry disposed within theinternal region, wherein the processing circuitry is in signalcommunication with the gas sensor.
 12. An explosion resistant housingcomprising: a sheet member-type enclosure; a cover which engages theenclosure forming a substantially closed internal region; a gas sensordisposed within the internal region; one or more openings providinggaseous communication between the internal region and an exterior of thesheet member-type enclosure; at least one support member, wherein the atleast one support member is separate from the enclosure and the cover,and wherein the at least one support member is coupled to at least oneof the enclosure or the cover.
 13. The housing of claim 12, furthercomprising: a base that engages the enclosure, wherein the at least onesupport member extends between the cover and the base and is coupled toboth the cover and the base.
 14. The housing of claim 13, wherein theenclosure comprises cylindrical metal sides and an integral end member.15. The housing of claim 12, further comprising: processing circuitrydisposed within the internal region.
 16. The housing of claim 12,wherein the one or more opening are disposed at an interface between thecover and the sheet member-type enclosure.
 17. The housing of claim 12,wherein the one or more openings comprise flame-proof joints.
 18. Anexplosion resistant housing comprising: first and second explosionresistant ends; a sheet member disposed between and retained by thefirst and second explosion resistant ends, wherein the first and secondexplosion resistant ends and the sheet member define an internal region;a gas sensor disposed within the internal region; one or more openingsconfigured to provide fluid communication between the internal regionand an exterior of the sheet member; reinforcing elements which extendbetween the first and second explosion resistant ends.
 19. The housingof claim 18, wherein the elements are in the internal region, or outsideof the internal region.
 20. The housing of claim 18, wherein the one ormore openings comprise flame-proof joints.